To meet the demand for wireless data traffic having increased since deployment of 4th generation (4G) communication systems, efforts have been made to develop an improved 5th generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post LTE System’.
The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like.
In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
SDN is a software technology of abstracting the concept of a network in a distributed or cloud system and providing a Quality of Service (QoS) through control and management for propagating data. The SDN technology is a technology for basically solving a network cost and complexity by providing a network-centric management technology through physically decoupling a controller with a switch.
SDN is a technology developed to improve speed, stability, energy efficiency, security, etc. in a software manner in a network system that depends on hardware such as an existing router or switch, etc. and is based on a concept called OpenFlow. OpenFlow is a technology of separating a packet forwarding function of a network equipment and a controller function by a standard interface and providing the openness of a network, and defines a packet data protocol among a controller and switches.
SDN decides a transmission path in accordance with each flow entry information of a switch. At this time, at network failure occurrence, if receiving a propagation of an event message propagated from the switch, a controller reflects corresponding message information, to generate new flow entry information for packet forwarding in accordance with a routing policy and algorithm of the controller and provide the corresponding flow entry information to the lower switches.
However, in the existing SDN, if network failure takes place, the corresponding switches frequently exchange event messages with the controller. Actual distances among the switches and the controller physically are distant away and therefore, a considerably large propagation delay is generated at the time of message exchange. Also, for the sake of flow entry information generation, even a processing delay for internal algorithm calculation is generated in the controller. These factors can become the cause of a considerable overhead at fast packet forwarding.
Owing to this, the following problems often take place in the SDN.
Firstly, according as the number of the switches to manage in the controller increases and the coverage of the controller gets wide, a physical distance between the controller and the switch gets distant away more and more. As a result, when the switch propagates a message to the controller at event occurrence, a propagation delay increases more and more.
Secondly, the controller performs the shortest path forwarding in accordance with an internal routing algorithm. However, due to a topology change by a Spanning Tree Protocol (STP), a topology change by link timeout, a flow expiration notification, and other various events taking place in the switch, an overhead can be generated in the controller and thus, lead to a result of making long a fail-over time at network failure occurrence. That is, to prevent the generation of a loop in the switch, the SDN closes a port of logical one portion of a redundant line, and again opens the closed port at problem occurrence in the corresponding port while propagating the topology change to the upper controller. Also, in case where a link in a topology table is not discovered a few seconds (for example, three seconds) or more, a change in the topology table due to link timeout is propagated to the controller. If a packet is not received during a constant time with respect to a specific flow and thus the corresponding flow is terminated, the SDN propagates a ‘Flow Removal’ message to the controller. And, the SDN propagates other various events that take place in the switch to the controller. The controller frequently receives such several events and re-calculates routing information and in accordance with the result, frequently updates (deletes and generates) a corresponding flow table to the lower switch, thereby providing a failure restoration operation. This finally causes a processing delay of the controller in itself, increasing a network processing cost.